Crosslinking process



Dec. 28, 1965 c. L.. KEHR ETAL CROSSLINKING PROCESS 5 Sheets-Sheet 1Filed OC'L. 24, 1962 Clifton L. Ke/Ir James L. Gaf/:rie

JNVENToRs Arij' Dec. Z8, 1965 c. L. KEHR r-:TAL

CHOSSLINKING PROCESS 5 Sheets-Sheet 2 Filed Oct. 24. 1962 CROSSLINKINGPROCESS 5 Sheets-Sheet 3 Filed Oct. 24, 1962 4 Clifton L. Kehr Jam'es L.Guthrie United States Patent O 3,226,356 CRUSSLHNQNG PRUCESS Clifton L.Kehr, liduor, and .lames L. Guthrie, Lain-ei, Md., assignors to W. R.Grace t Co., a corporation of Connecticut Fiied @et 24, 11262, Ser. No.232,771 3 Claims. (Cl. 26d-41) This invention relates to crosslinkedpolymers derived from a-olens and copolymers containing same and methodsof preparing same. More particularly this invention is concerned withcrosslinking polymers derived from aolens and copolymers containing sameat temperatures above their processing temperature at a rapid rate witha novel cross-linking system.

ln the field of polymers derived from a-olens, there is a continuingsearch for new and better cross-linking agents. Of special interest arethose which are unreactive at processing and compounding temperatures,but which can be triggered in some manner after the poiymer compound isprocessed into its final shape by molding, extruding or the like.

Thus in the polyolen art, there has been a long felt want forcrosslinking agents which not only crosslinlc at operable and economicaltemperatures above the processing temperature of the polymer orcopolymer but also crosslink at a rapid rate at said temperature so asto require a very short cure time.

ln a copending application having Serial Number 168,025, tiled Ian. 18,1962 and assigned to the same assignee, it has been discovered thatesters, both mono and di, of quinone dioxime are excellent crosslinleingagents for normally solid polyolens. Theonly drawback, however, is thatthe curing temperature is necessarily high, e.g. for polypropylene atemperature of 225 C. is necessary to obtain a suiciently high gelcontent in the polymer. Thus although the esters of quinone dioxime haveexcellent scotch (pre-cure) resistance at the high ternperatures (U5-200C.), such exceptional stability is not required, in fact, is not desiredin curing certain polymers derived from ct-oleiins and copolymerscontaining same.

For example a copolymer derived from a-oleiins which has recentlyentered the market on a commercial scale is the poly -olen copolymer,ethylene/propylene rubber (EPR). Because of low monomer cost, EPRpromises to be the rubber industrys lowest priced elastomer. Due to itsessentially nil double bond content, EPR is outstanding (relative toother vulcanizable elastomers) in its resistance to degradation byoxygen and ozone. For the same reason, however, EPR is rather diicult tovulcanize. For example, ethylene/ propylene rubber cannot be vulcanizedwith standard sulfur/accelerator receipes. Cornmercial manufacturers ofEPR currently recommend a dicumyl peroxide vulcanization recipe (usuallymodified with a small quantity of sulfur to minimize degradation of theEPR during the cure). This system, although operable, has the followingdisadvantages: (l) obnoxious odors from a combination of acetophenoneand mercaptan-like sulfur compounds, (2) high temperature/time curingcycles which are rather inflexible since there are no known acceleratorsor retarders for peroxides, and 3) the adhesion of the cured EPR to tirecords is extremely poor.

Gne commercial approach taken to overcome the disadvantages of EPR hasbeen the development of a sulfurcurable hydrocarbon rubber based onethylene and propylene. This product contains, beside ethylene andpropylene, a third monomer unit derived from a nonconjugated diene andis sold under the tradename Nordel by E. I. du Pont de Nemours and Co.,Inc. The resulting ice terpolymer after polymerization contains acontrolled degree of unsaturation which as in the case oi butyl rubber,serves as curing sites for vulcanization with standard sulfur-containingaccelerators. Although the odor problem is less critical by the use ofthis terpolyiner, the curing rate is still sluggish requiring a cure ofapproximately 3() minutes at 160 C. By ordinary rubber industrystandards, these conditions are too long and too high to be economicalfor general usage, especially in the tire industry.

The rubber tire industry generally desires a standard curing temperaturerange of -l50 C. for a period of no more than lO-2G minutes. Atprocessing temperatures below said range, the crosslinking orvulcanizing agents employed must be relatively non-scorchy but whenheated within said range the crosslinking agents must be able to rapidlycure the polymer. To employ orosslinking agents which cure attemperatures above the aforementioned range would be uneconomical forthe rubber tire industry as it would necessitate in many instances theintroduction of higher pressure steam generating units and a redesign ofpresent equipment to withstand the higher steam pressure.

Therefore, one object of this invention is to provide a novelcrosslinking system which effects curing of polymers derived froma-olelins and copolymers containing same, especially amorphouscopolymers such as EPR, in the range 130l50 C. at an operable ratewithout scorching (procuring during processing). In fact, this novelcrosslinking system is so versatile in the case of EPR that one can, byproper choice of curing agent and accelerator, formulate compositions sothat rapid and cornpiete crosslinking will occur at any predesiredtemperature ranging between the limits of 130 C. and 215 C. In addition,temperatures can be selected readily so that curing cycles of extremelyshort duration, eg. 2 minutes or less, can be achieved.

Still another object of the present invention is to provide a class ofsynergistic agents which when combined with the crosslinking agents andaccelerators therefor of this invention lower the curing temperaturestill further.

Other objects and advantages of this invention will become apparent froma reading hereinafter.

Summarily this invention relates to curing polymers derived from a-olensby admixing said polymers with a curing agent of the general formula,

wherein R is a member of the group consisting of benzoate, and analiphatic acyloxy group containing 1-20 carbon atoms and an acceleratorfor said curing agent comprising a Lewis acid or a Lewis acid precurserand heating said adrnixture to etect curing.

As used herein the term a-olen means a hydrocarbon monomer whichcontains a single terminally unsaturated grouping of the formula--CHICH2-l As used herein the term polymers derived from a-oletinsincludes coand terpolymers wherein at least 50 mole percent of thepolymer is derived from a-olens as herein deined. Thus, polymers derivedfrom `ot-oletins would include, but are expressly not limited to,polyethylene, polypropylene, ethylene/ propylene copolymers,ethylene/butylene copolymers, ethylene/ propylene/ diene terpolymers,and ethylene/ vinyl acetate copolymers, said latter two containing atleast 50 mole percent of the poly a-olefins. The polymers derived froma-olens as meant herein would also include polymers derived froma-oletins which had been further processed such as having beenchlorosulfonated, e.g. chlorosulfonated polyethylene as described in US.2,212,786.

"b J In this invention the term acyloxy means R- HJ-C o in which R' isan aliphatic group.

Substituents may be present in the ortho, meta and para positions of thebenzene ring of the benzoate 4group of the curing agent. Substituentssuch as halogens, alkyl groups, alkoxy groups, nitro groups, etc. areoperable. Also operable are other aromatic groups besides the benzenoidring. For example, quinone dioxirne esters of lor 2naphthoic acidfunction as well as similar esters of benzoic acid but in most cases aremore costly. The quinone dioxime esters of the aliphatic carboxylicacids, i.e. the aliphatic acyloxy-substituted quinone dioximes are alsooperable in substituted form. Substituents such -as the halogens have`been employed as will Ibe shown hereinafter.

In the present invention the term Lewis acid means a substance which canfill the valence shell of one of its atoms with an unshared pair ofelectrons from another molecule. Examples of Lewis acids include but arenot limited to AlCl3, FeCl3, SnCl4, ZnCl2, TiCl4, CrCl3, VCl4, AlBr37HgCl2, B133 and the like. Also included in this definition are mixturesof compounds which, when brought together in the polymeric compositionunder standard conditions of processing interact with each other togenerate the Lewis acid in situ. Also included in the definition ofLewis acids herein are Lewis acid coordination compounds which prior toaddition to the rubber compound have their maximum coordination numbersatisfied, but which in the course of compounding and curing interactwith the curing agent. Examples of this latter type of Lewis acidcoordination complexes are illustrated 'by ibut not limited to ferricacetylacetonate, aluminum acetylacetonate, boron fiuoride, n-butyletherate, zinc chloride: 2,Z-dithiobisbenzothiazole complex and thelike. The addition of said Lewis acid -accelerators to the system causesoptimum curing to occur (as shown by gel content of the polymer), attemperatures below the optimum curing temperature of the esters ofquinone dioxime per se as will be shown hereinafter.

In addition it has been found that the optimum curing temperature of thenovel curing agents and accelerators of the instant invention can, ifdesired, lbe lowered still further by adding to the system a synergisticagent consisting of a polar organic member of the group consisting ofcarboxylic acids, phosphoric acid, boric acid, and esters thereof.Examples of synergistic agents operable in the instant inventioninclude, but are not limited to, n-butyl stearate, tributyl citr-ate,tri-butyrin, tributyl phosphate, tributyl borate, stearic acid, and thelike.

The amount of crosslinking agent used in this invention is not criticaland can vary over wide limits `depending upon the polymer beingcrosslinked. Amounts of esters of quinone dioxime crosslinking agent inthe range 0.1-30 parts per hundred parts of polymer by weight preferably0.5-20 parts per hundred parts of polymer are employed.

The amount of Lewis acid accelerator used is in the range 0.005-1.0 partby weight per hundred parts of polymer and preferably 0.0l-0.5 part onthe same basis. The Lewis acid accelerator may, if desired, be added tothe compounding step as a solution (520% by weight) in suitablesolvents, for ease of handling and for uniformity of dispersion. Lowboiling organic solvents such as acetone, isopropanol, ethanol, benzene,and the like are operable. The solvent is boiled off in the compoundingstep.

The amount of synergistic agent employed herein is in the range 0.1-30parts per hundred parts of polymer lay weight and preferably 0.5-3.0parts on the same basis.

The polymer compositions to be cured in accord with the presentinvention may, if desired, include such additives as antioxidants,fillers, pigments, anti-static agents,

extending oils, plasticizers, tackifiers and the like within the scopeof this invention. Such additives are usually lbut not necessarily addedto the polymer composition by pre-blending prior to or during thecompounding step. Operable fillers would include carbon black, clay,silica, alumina, carbonates, oxides, hydroxides, silicates, diatomaceousearth, talc, kaolin, barium sulfate, calcium sulfate, calcium carbonateand the like. The aforesaid additives may he present up to 200 parts ormore per parts of polymer by weight and preferably 0.05-100 parts on thesaine basis.

Although the invention is operable with polymers derived frornot-olefins and copolymers containing same, Ifor ease of explanation andclarity the invention will, in the main, be explained using ethylene/propylene rubber (EPR) as the polymer to be cured.

The general procedure followed in performing this invention is to form acompound of the desired ingredients in a Banbury mixer, two-roll mill,Brabender Plastograph and the like at temperatures in the range 25-200C. The compounding temperature is determined by and is in excess of thesoftening point of the polymer but is below the curing temperatureexhibited vby the crosslinking agent. While milling the polymer aboveits softening point (which for EPR usually would be in the range .2S-C.)7 any filler and any synergistic agent are compounded in withcontinued milling. The crosslinking agent is then added followed by theaddition of the Lewis acid accelerator. It is possible to add all theaforementioned components together to the softened polymer but for moreuniform mixing and ease of handling, they are preferably added stepwise.The resulting compound is then processed into its final shape Iby anextruding or molding vstep under pressure at temperatures above thesoftening point of the polymer but below the curing temperatureexhibited by the crosslinking agent. This step is followed `by heatingthe shaped article to a higher temperature range, e.g. `for EPR -atemperature in excess of C. whereat rapid curing of the polymer iseffected. The curing temperature is dependent upon ymany factors,including (l) the polymer `being cured, (2) the actual crosslinkingagent and accelerator Within the classes disclosed and the amountsthereof, and (3) whether or not a synergistic agent is added. As ageneral rule the curing temperature employed for optimum curing, i.e.where the state of cure (percent gel) plateaus out, in the instantinvention is from 120 to 200 C.

The following examples are set down as yan aid in understanding theinvention but are expressly not designed to limit its scope. In theexample, unless otherwise noted, all parts and percentages are by weightper hundred parts of polymer.

Throughout the instant invention the melt indices (MI) were measuredunder the conditions specified in ASTMD l23S-52T, except for isotacticpolypropylene, in which instance the procedure was modified so that thetest was run at 230 C. instead of 190 C. The densities of the polymerswere measured under the conditions specifed in ASTMD 1505-57T. Thepercent gel content of the polymers in the instant invention wasmeasured by refluxing a weighed sample (approximately 0.5 g.) of polymerin a cellulose Soxhlet thimble in a suitable solvent (containing 0.3weight percent 2,6-ditertiary-butyl-4-methyl-phenol commerciallyavailable under the tradename Ionol from Shell Oil Corp. for 24 hours.The insoluble portion of the polymer sample after drying was weighed tocalculate percent gel as follows:

percent gel: 100

hydrocarbon content of the cured polymer. Suitable solvents for thepolymer compositions described herein include heptane, xylene,methylethyl ketone and the like, the only restriction being that theuncured polymer should be completely soluble in said solvent underconditions of the extraction procedure.

Mooney viscosity Was measured in accord with the conditions specified inASTMD-1646-61.

In all examples, unless otherwise noted, a Brabender Plastograph modelPL-V2 equipped with a recording unit for measuring changes in torque wasused for compounding. The compounded product was premolded into filmsamples of approximately mils thickness by pressing at temperaturesbelow the curing temperature for short intervals of time. Thesepremolded film samples of 20 mil thickness were then cut into smallerstrips of approximately 1.5 g. weight and then cured in a PasadenaPlaten Press at a pressure of G-1000 p.s.i. for

periods ranging from 1 to 15 minutes at various curing temperatures. Thesamples Were then removed from the press and cooled in air. Samples ofthe cured specimens Were then used to calculate the percent gel contentby the aforementioned solvent extraction method.

Table 1 shows a comparative study of the accelerating effect of variousLewis acid accelerators and synergistic agents on the crosslinking agentin curing ethylene/ propylene rubber (EPR). The compounding wasperformed in a Brabender Plastograph at -110 C. The components of thecompound were milled together over a period of l0 minutes. Samples ofthe compounded EPR were cured by placing them ina 6 6 0.02 mold andpressing them in a platen press for 15 minutes and 625 p.s.i at varyingcure temperatures. Weighed samples of the cured EPR were then measuredfor gel content in reuxing n-hepitane containing a small amount of anantioxidant :for 24 hours.

TABLE I Example No 1266 1450 1450 1450 1450 1450 1450 1450 1450 13871450 1450 27-1 129 12-4 12-22 12419 12-16 12-24 12-21 12-18 30-1 11e812-1 Compound 1 2 3 4 5 6 7 8 9 10 l1 12 Polymer b 100 100 100 100 100100 100 100 100 100 100 Crosslinking Ag Y Quinonedioximc llihenzoate 4.0 4. O 4. 0

Quinonedioxime bis(p-methoxybenzoate) Quinonedioxime bis(p-chlorobenzoate) Quinonedioximc Distearate Quinonedioximel)iheptanoatc Quinonedioxime Dihutyrate Quinonedioxime DiaectateQuinonedoxime bis (chloroacctate) Lewis acid accelerator:

Ferrie aeetylacetonate synergistic Agent:

Percent gel of cured polym r at c S2 81 6h 81 S3 39 79 81 b1 78 77Example No 1387 1450 1450 1450 1450 1450 1450 1450 1450 1450 1450 145039-10 11-9 12-0 12-11 12-7 12-2 1213 12-10 12-5 12-12 12-8 12-3 Compoundn 13 14 15 1G 17 18 20 10 22 23 24 Polymer b 100 100 100 130 100 100 100100 100 100 100 100 Crosslnking Agen Quinonedioxime DibenzoateQuinonedioxime bis(p-metl1oxybenzoate) Qunoncrlioximebis(p-ehlorobcnzoatc) Quinonedioxime Distcarate QuinonedioximeDipheptanoate Qulnonedioxiine Dibutyrate Quinoucdioxime D acetnteQulnoncdioxime bis(chloroacetate) Lewis acid accelerator:

Ferrie acetylacetonate Synergistie Agent:

Tributyl borate Tributyl phospl Percent gel of cured polymer at c 1 0 11 0 1 O l 1 1 72 0 G3 69 0 1 30 0 l 0 68 43 77 80 33 G6 (19 l 6 3 83 5177 83 56 G9 74 24 35 85 G3 84 87 66 70 S1 41 5() 43 See footnotes at endof table.

Example No 1387 1387 1387 1387 1007 1450 1007 1387 1387 1206 7-11 23-23-5 23-7 38-18 12-15 38-17 38-8 7-15 313 Compound 1 25 26 27 28 29 303l 32 33 34 3a Polymer b. 100 100 100 100 100 100 100 150 d 100 100 150e Crosslinking Agent:

Quinonedioxime Dibenzoate 4. 4.0 2.0 8.0 4.0 4.0 4, 0 4.0 4 0Quinonedioxime bix(prnethoxybenzoate) Quinonedioxime bis(p-chlorobenzoate) Quinonedioxime Distearate QuinonedioximcDipheptanoatc. Quinonedioxime Dibutyrate Quinonedioxime DiaeetateQuinonedioxime bis(chloroacetatc) Lewis acid accelerator:

Ferrie acetylace synergistic Agent:

Stearic acid Tributyl citrate Tributyl borate Tributyl phosphate Percentgel of cured polymer at '1 Compound admixed in a Brabender Plastographat 80-110D C. for 5 minutes.

b Ethylene/propylene rubber (E.P.R.) containing 58;!:5 mole percentethylene.

ERR. percent gels measured after reiluxing sample for 24 hours inn-lieptane containing 0.3 weight percent, 2,0-

15 minute curing time. ditertiary-butyl-4mcthylphenol.

Mooney viscosity ML (212 F) =42.

d 100 parts ethylenc/propylene rubber containing 585:5 mole percentethylene admixed with 50 parts Sterling MT carbon black. C 100 partsethylene/propylene rubber containing 58:1;5 niole percent ethyleneadmixed with 50 parts Spheron 9 carbon black.

As is readily seen in Table I, the addition of a Lewis acid acceleratorto the curing agent of this invention causes curing at a lowertemperature range than the crosslinking agent per se; compare, e.g.compounds l and 2 or 4 and 5 `and the like. In addition it is to benoted that the Iaddition of a synergistic agent to the compound causescuring to occur at a still lower temperature than the combination ofcuring agent and accelerator; compare, e.g. compounds 2 and 3. Theaddieect of a Lewis acid accelerator i.e. ZnCl2 and a synergistic agenti.e. tributyl citrate on a curing agent, quinone dioxime dibenzoate(DBGMF) for ethylene/ propylene rubber (EPR).

5 FIGURE Il shows the accelerating effect of various Lewis acidaccelerators on the curing agent, quinone dioxime dibenzoate (DBGMF) forcuring EPR in the presence of various synergistic agents. In all cases,curing occurred at a lower temperature in the presence tion of thesynergistic agent to the curing agent withof an accelerator than occurswith solely a curing agent. out any `accelerator appears to give only amarginal im- Table Il shows a comparative study of the acceleratingprovement in lowening the curing temperature; compare eiect of the Lewisacid 'accelerators and synergistic agents compounds 1 and 31. However,when the accelerator on the crosslinking of various polymers derivedfrom is added to the curing system a substantial lowering olens. Thecompounding was performed during a I0 of the curing temperature isobtained. This is readily minute milling period in a BrabenderPlastograph at ternapparent from FIGURE I which shows graphically theperatures ranging from 10-30 degrees centigrade above TABLE II 951 1450951 1450 1450 1450 1007 1450 1450 1450 1450 1450 Example No 11-3 1-325-3 1-4 31-1 31-3 28-12 28-14 1-5 1-6 l-7 28-17 Compoundn PolymericMaterial Polyethylene b Polypropylene Ethylene/butylene copolymer dClilorosulfonated polyethylene D Ethylene/propylene/dienc terpolynicr fEthylene/vinyl acetate copolymer 11 Crosslinking Agent:

Quinone dioxime dibenzoate Lewis Acid Accelerator:

FeCl3 Ferrie acetylacctonate synergistic Agent:

Stearic acid. 1. 0 1. 0 1. 0 Tributyl citrate 1. 0 1. 0 1. 0 Percent gelof cured polymer at h:

C- 3 13 0 19 2 67 0 37 0 0 C. O. 6 50 0 0 49 67 75 l 75 l 69 200 C 47 530. 6 43 53 79 8G 79 77 G2 74 225 C.. 55 60 5l 55 8l 87 76 67 77 Compoundadmixed in a Brabender Plastograph for 5-10 minutes. Rubbers milledfat80-110o C.; thermoplastic polymers milled at 15-25" C. above theirmelting point.

1Polyethylen density 0.96 g./cc., melt index 0.7 and 137 C. meltingpoint. n Polypropylene; density 0.899 g./ce., melt index 4.4 and 172-173C melting point.

Ethylene/butylene copolymer containing 1.0 weight percent butylenc;density 0.93 g./cc. e Chlorosulionated polyethylene rubber, specificgravity 1.12428, sold under tradename IIypalon 20, E. I. du Pont & Co.,Ine. i Ethylene/propylene/diene terpolymer rubber, speciiie gravity0.85, sold under the tradename EC D-330", E. I. du Pont & C0., Mooneyviscosity a Ethylene/vinyl acetate copolymer containing 72 weightpercent ethylene; density 0.95 g./ec. at 30 C, sold under the tradcnameElvax 250, E. I.

du Pont z Co., Ine., melt index 15 h 15 minute curing period.

Percent gel measured after refluxing weighed sample for 24 hours inxylenc for polyethylene, polypropylene, ethylene] butylene copolymer andethylene/vinyl acetate copolymer; in methyl ethyl ketone forchlorosulfouated polyethylene and in n-heptaue for ethylene]propyleue/diene tcrpolymer. All reuxiug solvents contain 0.3 weightpercent 2,0-ditertiary-butyl-4-1netliyl phenol.

the softening point of the thermoplastic polymers and at S110 C. for therubbers. Samples of the polymers were shaped into 6" 6 0.02 tensileplaques in a platen press for 1 minute at 12S-165 C., depending on thesoftening point of the thermoplastic polymer, and atmospheric pressure,followed by a 2 minute press at l25- 165 C. and 625 p.s.i. pressure. Thesamples were removed from the mold and cured in a platen press forminutes at 625 p.s.'i. and varying curing temperatures. Weighed samplesof the cured polymers derived from olens were then measured for gelcontent in suitable reiluxing solvents containing a small amount of anantioxidant for 24 hours. The rubbers in Table Il were cured yandmeasured for percent gel in the same manner as the EPR in Table I exceptthat for chlorosulfonated polyethylene the solvent used was methyl ethylketone.

The results in Table II show the operability of the Lewis acidaccelerators and the synergistic agents of this invention in loweringthe curing temperature of the curing agent for various polymers derivedfrom zx-olefins.

FIGURE III shows a comparison of the curing system of the instantinvention with the presently recommended commercial curing system forethylene/propylene rubber (EPR) for l5 minute curing periods. Thepresent commercially recommended curing system for EPR consistsessentially of dicumyl peroxide with a small amount of sulfur tominimize degradation during the cure. Zinc oxide (ZnO) is added tocreate a neutral or basic environment for the dicumyl peroxide andcalcium stearate is added as a processing aid to prevent scorch. FromFIGURE III is it readily seen that the curing system of the instantinvention causes curing to occur at a lower temperature and to a highdegree within the preferred curing temperature range of l30-150 C. forEPR.

We claim:

1. A curable composition consisting essentially of 100 parts by Weightof a polymeric material containing :at least 50 mole percent of apolymer derived from an aolelin, said polymeric material being selectedlfrom the group consisting of polyethylene, polypropylene,ethylenebutylene copolymer, chlorosulfonated polyethylene, ethylene,ethylene-vinyl ace-tate copolymer and ethylene-propylenedieneterpolymer, 0.1 to 30 parts/ 100 parts of said polymeric material byweight of a curing agent of the general formula:

wherein R is a member of the group consisting of benzoate and analiphatic acyloxy group containing 1 to 20 carbon atoms and 0.005 to 1.0part/ 100 parts 0f said polymeric material by weight of a Lewis acidselected from the group consisting of FeCl3, ferrie acetylacetonate,A1Cl3, ZnCl2 and SnC-l4-5H2O.

2. A curable composition consisting essentially of 100 parts by weightof a polymeric material containing at least 50 mole percent of a polymerderived from an aolefin, said polymeric material 'being selected fromthe group consisting of polyethylene, polypropylene, chlorosulfonatedpolyethylene, ethylene-butylene copolymer, ethylene-vinyl acetatecopolymer and ethylene-propylenediene terpolymer, 0.1 to 30 parts/ 100parts of said polymeric material by weight of a curing agent of thegeneral formula:

wherein R is a member of the group consisting of benzoate and analiphatic acyloxy group containing 1 to 20 carbon atoms, 0.005 to 1.0part/ parts of said polymeric material by weight of a Lewis acidselected from the group consi-sting of FeCl3, ferrie acetylacetonate,AlClB, ZNClZ and SnCl4-5H2O and 0.1-30 parts/100 parts by weight of saidpolymeric material of a synergistic agent for curing said polymericmaterial consisting -of a polar organic member of the group consistingof carboxylic acid, phosphoric acid, boric acid and esters thereof.

3. The method of curing polymeric material containing at least 5 0 molepercent of a polymer derived from an a-olen, said polymeric materialbeing selected from the group consisting of polyethylene, polypropylene,chlorosultonated polyethylene, ethylene-butylene copolymer,ethylene-vinyl acetate copolymer and ethylene-propylenediene terpolymercomprising mixing together 100 parts by weight of said polymericmaterial, 0.1 to 30 parts/ 100 parts of said polymeric material byweight of a curing agent of the general formula:

wherein R is a member of the group consisting of benzoate and analiphatic acyloxy group containing 1 to 20 carbon atoms and 0.005 to 1.0part/100 parts of said polymeric material by weight of a Lewis acidselected from the group consisting of FeCl3, ferrie acetylacetonate,A1Cl3, ZnClz and SnCl4'5H2O and thereafter heating the resultant mixtureto eiect curing of said polymeric material.

4. The method according to claim 3 wherein a synergistic agent forcuring said polymeric material consisting 1of a polar organic member ofthe group consisting of carboxylic acids, phosphoric aci-d, boric acidand esters thereof is added to the mixture prior to heating said mixtureto effect curing of said polymeric material.

5. The composition according to claim l in which the Compositioncontains in addition, 0.05 to 200 parts/ 100 parts of said polymericmaterial by weight. of a ller for said polymeric material.

6. The composition according to claim S wherein the tiller is carbonblack.

7. The method according to claim 3 wherein 0.05 to 200 parts/ 100 partsof said polymeric material by weight of a filler for said polymericmaterial is added to the mixture prior to heating said mixture to eifectcuring of the polymeric material.

8. The method according to claim 7 wherein the ller is carbon black.

References Cited by the Examiner UNITED STATES PATENTS 2,748,104 5/1956Viohl 260-41 3,012,020 12/1961 Kirk et al 260-41 3,093,614 `6/1963MacKenzie et al 260-41 OTHER REFERENCES Morton: Introduction To RubberTechnology Reinhold, New York, 1959, pages 323-324.

MORRIS LIEBMAN, Primary Examiner. LESLIE H. GASTON, Examiner. K. B.CLARKE, A. LIEBER'MAN, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,226,356 December Z8, 1965 Clifton L. Kehr et al It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Columns 5 and 6, TABLE I, under the heading "Example No. 1450 lZ-l3,line l, for "29" read 19 same table, under the heading "Example No. 1450lZ-lO2 line l, for "l0" read 20 column 9, lines 4l and 42, Strike out"ethylene,".

Signed and sealed this 25th day of October 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents AttestingOfficer

1. A CURABLE COMPOSITION CONSISTING ESSENTIALLY OF 100 PARTS BY WEIGHTOF A POLYMERIC MATERIAL CONTAINING AT LEAST 50 MOLE PERCENT OF A POLYMERDERIVED FROM AN AOLEFIN, SAID POLYMERIC MATERIAL BEING SELECTED FROM THEGROUP CONSISTING OF POLYETHYLENE, POLYPROPYLENE, ETHYLENEBUTYLENECOPOLYMER, CHLOROSULFONATED POLYETHYLENE, ETHYLTENE, ETHYLENE-VINYLACETATE COPOLYMER AND ETHYLENE-PROPYLENEDIENE TERPOLYMER, 0.1 TO 30PARTS/100 PARTS OF SAID POLYMERIC MATERIAL BY WEIGHT OF A CURING AGENTOF THE GENERAL FORMULA: